fix #8888 - set `java.util.Arrays.useLegacyMergeSort``to true in JNLP files to avoid "Comparison method violates its general contract" errors in Java 7

git-svn-id: http://josm.openstreetmap.de/svn/trunk@6079 0c6e7542-c601-0410-84e7-c038aed88b3b
Merge branch 'master' into mirror